Tuesday, October 11, 2005

Well, here's my apparently monthly post for October. Over the course of September I've been teaching motion (like most Physics teachers). I've been relying heavily on Vernier sensors to do it. The most useful by far this month has been the motion detector.

You can use these with the Ti-83/84 graphing calculators or with computers by interfacing with a LabPro (or CBL for calculators). Data collection is very easy and students can see a graph of motion in real time. On the computers they can actually see a graph of position and velocity simultaneously. For visual learners this is invaluable. Anyway, here are a list of labs I've doen with probeware in the past month:

Distance Graph Match: Using CBL's and calculators (can be done with LabPro's and computers) with the motion detector. One student views a distance time graph while the other stands in-front of the motion detector. The student viewing the graph then directs the other student to move forward or back and at what speed to move. The goal is to have the graph created by the moving student match the given graph. With a little practice they get pretty good.

They've all seen these graphs before, but many have never really thought about the motion before. This way they have no choice but to think about it.

Velocity Graph Match: As above, but now velocity is important, not position. For this one it works better for the mover to see the graph while moving. My students also found it easier to move a book up and down above the motion detector.

Coffee Filter Lab: Using the motion detectors and LabPros with laptops (can be done on calculators, but is nore difficult). Students find the terminal velocity of a falling coffee filter. They need to find a straight line portion of the distance graph and determine the slope of the line (easy in LoggerPro, the software interface for the LabPro). They then repeat with two filters together, and then three, and then....all the way up to 10.

I then have the students graph the Velocity vs. Number of Filters and fit an equation to their graph. They almost always pick a straight line and then we talk about the implications for that (add enough filters and it would be falling at the speed of light). The more savvy students will realize it is a curve and fit a quadratic function to it. This, of course, is also incorrect. If they do this have them zoom out their graph to see that when they add about 30 filters they will just float in the air and not fall.

Finding g Two Ways: We used the slope of the distance graph to find velocity, now its time to find the slope of a velocity graph to find acceleration. Students use a motion deterctor to track a falling object. For this I recommend holding the detector high in the air facing down so you won't have to buy new ones abter your students drop their textbook on them. To get best results the detector should be comptely level. I've found if students are careful they can do a pretty good job simply holding the detector in their hands, but you may want to use the mounting clamps included to get more exact/repeatable results.

The second way we find g is with a photogate and a picket fence. This is really easy and gives incredibally precise data. You can buy picket fences or you can make your own. I went to the neighborhood hardware store and got them to give me a few plexiglass scraps. I used electrical tape for my black bands. Total cost: $0 as I already had a roll of tape (they cost $5 from Vernier).

My longest post so far:I'm now into Newton's Laws and a new batch of labs. I'll post those up soon. I should also mention that I do video analysis labs of motion with LoggerPro as well as old traditional non-technology based labs.

3 comments:

I do all of this with PASCO, which is basically the same thing as Vernier. Personally, I can hardly hold my enthusiasm in class, because it is such a great visualization of what velocity really is.

This was much tougher to explain in the old days, especially for the disinterested student. I think I take half the time in 1-D motion than I did before I had this stuff, and it carries over to taking less time with 2-D motion.

I say that every school should be trying to find a way to afford this stuff.

I've not used PASCO, but I agree virtually any variety of probeware really enhances teaching for understanding.

Even though you don't have Vernier stuff, you may still want to give the LoggerPro software a look. Even though you don't need it for your probeware.

LoggerPro also does video analysis. Students are able to track motion of an object and get position and velocity graphs with ease. They can also display velocity vectors on the video as well. I find this particularly helpful with 2-D motion.

Plus it's relatively cheap. Form the Vernier website: "For only $149, Logger Pro includes a generous site license that allows a school or a college department to install Logger Pro on every school computer, all instructor computers, AND the students' home computers."

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I am currently the Director of Instructional Technology at Divine Child High School. Additionally I teach an Electronics with Micro-controllers class and I am very interested and involved in physics education in Michigan.

I am an active member of both the Detroit Metropolitan Area Physics Teachers and the Michigan Section of the American Association of Physics Teachers and maintain the websites for both organizations.